The present invention relates generally to printing and more particularly to managing poorly compressible images in a resource limited system.
Certain conventional printing systems utilize electronic precollation (EPC) memory to store print jobs that have been decomposed and compressed. EPC memory supports a xe2x80x9cscan once, print manyxe2x80x9d printing model where a document is scanned into a system a single time and then multiple copies of the document are distributed to multiple printers for printing. EPC memory is often found in print servers or in digital front ends (DFEs).
EPC memory typically works quite well when black and white images are being printed. The memory and bandwidth requirements for printing such black and white images are not excessive. Color images encoded in accordance with a CMYK color model, however, have four-times the amount of data as black and white images. Thus, the printing of color images has posed a strain on the memory resources and computational resources of some conventional printing systems. Matters are complicated by the current trend of requiring increased throughput in conventional printing systems that use EPC memory.
The present invention addresses the above-described limitations of conventional printing systems. The present invention seeks to balance throughput requirements, memory requirements and image quality requirements. In one embodiment of the present invention, each page of a document is decomposed into four color separations. The sizes of the compressed color separations are compared to the available memory in an EPC system to determine whether sufficient memory in the EPC system is available for printing the page in an interleaved printing mode. In the interleaved printing mode, like color separations from consecutive pages are printed together. Thus, the cyan color separation from the first page is printed followed by the cyan color separation from the second page. Subsequently, the magenta color separation from the first page is printed followed by the magenta color separation of the second page. If the color separations are too large, it may be difficult to transfer the separation data quickly enough. If the size of the separation is too large, the throughput is insufficient to transfer the data in the separation in a timely fashion. This arises since the compressed color separations for the second page are also stored in the memory of the EPC system in the interleaved printing mode. For such large color separations, the page is printed in accordance with a single page printing mode where the separations for a single page are printed consecutively.
Prior to printing the page in the single page printing mode, a check is made whether the color separations of the page occupies too much memory, even when printed in accordance with the single page mode. A determination is also made whether the separation is too large to satisfy throughput requirements. If the determination indicates that the separation is too large, the page resolution is reduced, and an approach is used to reduce the amount of data stored for the page by decreasing the resolution of the data.
In accordance with one aspect of the present invention, a method is practiced in a digital color printing system that has a storage for storing pages to be printed. The storage includes memory having memory space. The system also includes an image output terminal (IOT) for producing image output. This memory holds a selected page that includes at least two color separations of distinct types containing color data. In accordance with the method, an amount of color data contained in the color separations is determined and an amount of memory space available in the memory for use in printing the selected page is determined. Based on these determinations, it is determined whether to print the selected page in an interleaved mode wherein color separations of like types from separate pages are collated together to be printed successively prior to printing other types of color separations from the separate pages.
In accordance with another aspect of the present invention, a digital color output system includes an IOT for generating output from pages containing color separations holding image data. The IOT outputs in an interleaved printing mode wherein color separations from consecutive pages are output together. The system also includes an electronic precollation (EPC) system for storing image data prior to outputting and for passing input data to the IOT for outputting. The EPC system has a memory with a quantity of available memory space. The system also includes a mode selector for selecting whether a selected page is output in the interleaved printing mode based on how much image data is contained in the color separations of the selected page and the quantity of available memory space in the memory of the EPC primary storage.